Since the Great Dismal Swamp accident in 1986 NS steam has been restricted to 40mph. But recently on one of the Knoxville-Asheville 630 trips that I chased, we chased her and paced side by side no gain at 50mph or better. But on 765's recent trips she seemed to be running at only around 40 on some of the videos I have seen. So is it just that it is not as strict as it used to be, or is it special order or what?

I would say your speedometer among other things is probably off.

I didn't time any of the miles on these trips, but felt like we were running a little faster Saturday AM than the rest of the time. Just my opinion. I seem to recall that the diesel assist that morning was possessed by the devil and was left DOA in the yard in Asheville after an attempted but failed exorcism. Perhaps its demons were a contributing factor.

I see many variables here -- among other things, I'd bet a fair amount of money that the speedometer on 630 is calibrated much more often and with a greater degree of scrutiny than the one in "Southern 154's" motor vehicle. I do think the 40 MPH is still the official party line (i.e. company policy) for tea kettles. It would also be my opinion that most all of the tea kettles out on the NS mainlines can safely function at a speed higher than 40.

DISCLAIMER: Not a steam guy, didn't stay at the Holiday Inn Express last night.

49 CFR 229.117 says (loose paraphrase) +/- 5 MPH accuracy on spedometers at speeds over 30 MPH.

ETA

Great.......

If you have proof of this, I'd like to see it, last time I checked, 630's bearings didn't like speeds over 40.

When I rode a 630 trip last spring the GPS on my phone said 40MPH right on the dot.

Yes, the 40-mph restriction is what the NS rule book says still for "All steam locomotives", last time I checked, and that's what I clocked 765 at on "Pacer's Paradise" east of Huntington, Pa. last year. My cars' speedometers agree precisely with the speed radar signs erected hither and yon to reprimand drivers into driving at safe speeds around school zones and residential neighborhoods.

However, rules are apparently bent with executive approval. I distinctly remember at least two occasions after the 40-mph limit was imposed where I "clocked" 611 in excess of 55 mph; both were instances of running late and trying to make up time and/or get out of the way of priority trains on single track, at sunset or just after dusk, on ramrod-straight trackage.

I also recall published reports that the Chessie Steam Special/Safety Express had an official speed limit of 55 mph. And I similarly remember people with stopwatches timing the last laps from Connellsville back to Pittsburgh after sunset in July 1981 at somewhere above sixty...... once again, trying to make up some lost time.

I would suggest that the increased prevalence of GPS and cell-phone communications will make "getting away" with such "rule bending" much more problematic in the modern era, as opposed to still needing stopwatches in 1991 when I rode behind an LNER A4 on the high side of 85 returning from Holyhead to Crewe.......

Maybe our speedometer was off, and we chased the Saturday Morning trip like etalcos rode. The second scene in the below video looks like it is above 40 at Jefferson City (and possibly the 4th scene in Del-Rio), but you can be the judge, again thanks for the input. Very good video if you have not watched it, not mine though.
https://www.youtube.com/watch?v=0EQERd2NJYs

Furthermore if you are riding the train on former Southern Railway territory and trying to time speed by milepost you should take a close look at your track charts. Not a single one of those mileposts are 5280 feet apart. Some of them a several hundred feet off.

This is true almost anywhere you go, save for a brand-new transit line. Thus, many railroads have "Measured Mile" segments highlighted in the employee TT that specify an exact mile segment, often level and straight, to be used to time the train and check the speedometers.

In Britain you could even purchase booklets that covered various sections of the country telling you exactly how many feet, or rods and chains, there were between official mileposts on the rail lines in the UK. These were aimed at the segment of the rail enthusiast fraternity obsessive-compulsive enough to measure locomotive performance by timing trains with precision and calculating speeds and acceleration thereof.

I had one guy that used to calculate the circumference of a steam loco driver and extrapolate the speed from the audible RPM based on the exhaust beats. He was good enough to figure out that at least one tape recorder I had used on one trip ran slightly underspeed the whole time even on the recording car's 110-volt AC line, explaining a discrepancy between alleged measured speeds and the speeds discerned by the recorded sounds.

In this age of real-time computer telemetry from locomotives to the Road Foreman's laptop, any engineer, or pilot engineer, who values his job and certification is not going to risk it for "giggles and grins", just to see what 630 or 765 "can do". That "plus-or-minus 5 mph" rule of thumb assumes a brief, unintended bump-up in speed, most likely due to a run-in of a heavy tail on a long, heavy freight train on a down grade, and it requires the engineer to take immediate action to bring his speed back down as quickly as safely possible. You can't be a "cowboy" engineer in the computer age, at least not for long. I would chalk-up reports of contemporary speeding by steam specials as urban legend, unless the accuser can produce the telemetry printout.

I'd like to see your proof of this. Perhaps the last time you checked was when she was still on grease lubricated bearings.

GPS speedometers are also fun to watch. I've noted some opportunities to gain on the schedule on some of the 21st Century Steam Program trips that I have worked over the last two years.

This discussion got me thinking about the top speed of the SOU 630 given its 57-inch drivers and friction bearings. We all know that high speed locomotives have larger diameter drivers which effectively slows the rotation of the wheels at any given speed. At 40MPH the 630's drivers are turning at 236 RPM. In contrast, the UP 3985 with roller bearings on 69-inch drivers is turning at 194 RPM at 40 MPH and we know that 3985 can easily run at modern 70MPH track speeds with its wheels turning at 341 RPM. Is there a physical speed limit, in RPM, for locomotives with conventional bearings?

Funny. Ironically I did stay at a Holiday Inn Express last night, and when I woke up they had sold out and it is now a Red Roof Inn. True story.... Maybe one of these days I'll be riding behind/chasing 611 and during the middle of the trip the +40mph ban will be lifted....

FYI, I rode the crew car behind 1218 from jacksonville to Valdosta in December of 1987 and I clocked the mileposts coming back that evening, and we were going well over 40...
This of course was after the swamp derailment and the speed restrictions were in place.